1. Field of the Invention
The present invention relates to an endoscope system that picks up images of inside of a hollow organ based on autofluorescence generated from living tissue, acquiring image data used to determine whether the living tissue is biologically normal or abnormal. The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-239925 (filed on Aug. 8, 2000), which is expressly incorporated herein by reference in its entirety.
2. Description of the Related Art
FIG. 14 is a block diagram of a conventional endoscope system. The endoscope system is composed of an endoscope 70 and an external unit 80. The endoscope 70 has a light distribution lens 71 and an objective lens 72 installed at its distal end. Additionally, this endoscope 70 has a light guide 73 that is a fiber bundle. The light guide 73 is led through the endoscope 70, such that its distal end faces a light distribution lens 71, while its proximal end is arranged to lead into the interior of the external unit 80. Further, the endoscope 70 is installed with an ultraviolet-and-infrared cut-off filter 74 and a CCD (charge-coupled device) 75. An imaging plane of this CCD 75 is arranged near a point at which objective lens 72 focuses an image of a subject when the distal end of the endoscope 1 is placed to face the subject. The ultraviolet-and-infrared cut-off filter 74 is set in an optical path between the objective lens 72 and the CCD 75.
The external unit 80 comprises a white light source 81 for emitting white light as a collimated light beam and an excitation light source 82 for emitting a collimated light beam, including wavelength components in the ultraviolet region. Along the optical path of the white light emitted from the white light source 81 are provided an infrared cut-off filter 83, a first shutter 84, and a dichroic mirror 85, arranged in this sequence. The infrared cut-off filter 83 blocks wavelength components in an infrared spectrum of the white light emitted from the white light source 81, at same time transmits wavelength components in a visible spectrum. The first shutter 84 intermittently blocks or transmits the white light that has passed through infrared cut-off filter 83. The dichroic mirror 85 transmits wavelength components in the visible spectrum of the light entering thereto, while reflecting wavelength components in the ultraviolet spectrum of the light. Thus, the white light in the visible spectrum that has passed through the first shutter 84 then passes through the dichroic mirror 85.
The excitation light source 82 is arranged so that light emitted therefrom orthogonally crosses the optical path of the white light passing through the dichroic mirror 85. Along the optical path between this excitation light source 82 and the dichroic mirror 85 are provided an excitation light filter 86 and a second shutter 87, arranged in this sequence from the excitation light source 82. The excitation light filter 86 transmits only those wavelength components in the spectrum that can be used as excitation light. Note that the excitation light refers to ultraviolet light capable of exciting living tissue to cause autofluorescence. The second shutter 87 intermittently blocks or transmits the excitation light that has passed through the excitation light filter 86. The excitation light that has passed through this second shutter 87 is reflected by the dichroic mirror 85, and the optical path of the excitation light reflected by the dichroic mirror 85 coincides with the optical path of the white light that has passed through this dichroic mirror 85.
In the optical path downstream of the dichroic mirror 85 are provided a diaphragm 88, a wheel 89, and a condenser lens C, arranged in this sequence. The diaphragm 88 controls the quantity of light passing therethrough. The wheel 89 is formed in a disc shape, on which four openings (not shown in the figure) are formed along its circumference. Into each of these openings are fitted a blue filter transmitting only blue light, a green filter transmitting only green light, a red filter transmitting only red light, and a transparent member transmitting the excitation light, respectively. Rotated by a motor, this wheel 89 repeatedly inserts the blue, green, and red filters and the transparent member into the optical path in sequence.
During the interval for which any one of the blue, green, or red filters of this wheel 89 is inserted into the optical path, the first shutter 84 transmits the white light while the second shutter 87 blocks the excitation light. Thus, in these times, only white light enters the dichroic mirror 85. This white light is then adjusted in amount of light by the diaphragm 88, sequentially converted into blue light, green light and red light by the blue filter, green filter and red filter of wheel 89 respectively, and enters the condenser lens C. On the other hand, during the interval for which the transparent member of this wheel 89 is inserted into the optical path, the first shutter 84 blocks the white light while the second shutter 87 transmits the excitation light, so that only the excitation light enters the dichroic mirror 85. The excitation light is then adjusted in amount of light by the diaphragm 88, passes through the transparent member of the wheel 89 and enters the condenser lens C.
This condenser C converges the light falling thereon onto the proximal end face of the light guide 73. Accordingly, the blue light, green light, red light and the excitation light repeatedly enter this light guide 73 in sequence. Light entering the light guide 73 is guided thereby and distributed by the light distribution lens 71. When the distal end of the endoscope 1 is positioned to face the subject, this subject is sequentially illuminated or irradiated by the blue light, the green light, the red light and the excitation light. Whenever this subject is illuminated by the blue light, the green light or the red light, the objective lens 72 forms an image of the subject by the blue light, the, green light or the red light in a plane with the imaging plane of the CCD 75. These images are converted into image signals by the CCD 75. More specifically, the images of the subject respectively formed from the blue light, the green light and the red light are converted into blue, green, and red image signals, respectively.
The subject generates autofluorescence when irradiated by excitation light. The autofluorescence generated from the subject and excitation light reflected by surface of the subject enters the objective lens 72, which forms an image of the subject on the imaging plane of the CCD 75. Note that, since the ultraviolet-and-infrared cut-off filter 74 is set in the optical path between the objective lens 72 and the CCD 75, the image that consists only of the autofluorescence form the subject is focused onto the imaging plane. This CCD 75 converts an image of the subject formed from the autofluorescence into an image signal (a fluorescence image signal).
Further, the external unit 80 has an image processing part 91 connected to the CCD 75 through signal wires. This image processing part 91 receives blue, green, red and fluorescence image signals output from the CCD 75 in sequence. This image processing part 91 synthesizes a color image of the subject (normal image) based on the blue, green and red image signals. Moreover, this image processing part 91 generates a fluorescence image of the subject based on the fluorescence image signal.
Thus, the conventional endoscope system has two light sources 81, 82 for emitting visible light (blue, green, and red light) and excitation light. More specifically, the conventional endoscope system has a normal light source 81 for emitting white light and an excitation light source 82 for emitting excitation light. Normally, these two light sources 81, 82 are both turned on continuously. Note that light sources 81, 82 have greater electricity requirements than other endoscope components, which makes it difficult to reduce the power requirements of such endoscope system that includes two light sources 81, 82.
Further, in this endoscope, since the light flux emitted from the two light sources is introduced to single light guide 73, a fixed space is required to implement the optical system, which frustrates efforts to reduce the bulk of the endoscope device.
It is the object of the present invention to provide an endoscope system with a single light source capable of alternately irradiating the subject with illumination light for acquisition of color images and with irradiation light for acquisition of fluorescence images.
The endoscope system according to the present invention comprises a light source for emitting light, including visible wavelength components and an ultraviolet wavelength component to excite autofluorescence from living tissue, a light guide arranged along an optical path of the light emitted from the light source that guides the light to irradiate a subject, a first filter mechanism that has a first filter transmitting ultraviolet light and first color light which is one of blue, green and red light, a second filter transmitting second color light which is one of the red, green and blue light other than the first color light and a third filter transmitting third color light which is remain of the red, green and blue light and that sequentially and repeatedly inserts the filters into the optical path between the light source and the light guide, a second filter mechanism that intermittently inserts a fluorescence observation filter transmitting ultraviolet light, while blocking the first color light into the optical path between the light source and the light guide, an objective optical system for forming an image of the subject surface by focusing wavelength components except the ultraviolet light from the subject irradiated by the light guide, an imaging device that picks up the image of the subject formed by the objective optical system and converts it into a image signal, and a processor. The processor generates normal image data that is color image data, based on the image signals obtained by the imaging device during a period in which the first filter is inserted into the optical path, during a period in which the second filter is inserted into the optical path, and during a period in which the third filter is inserted into the optical path, respectively, while controlling the first filter mechanism with the fluorescence observation filter retracted from the optical path, and also generates fluorescence image data based on image signals obtained by the imaging device during a period in which the first filter is inserted into the optical path while controlling the first filter mechanism with the fluorescence observation filter inserted into the optical path.
The first filter mechanism and the second filter mechanism may be arranged along the optical path in this order from the light source side. In this case, light emitted from the light source is converted into a mixture of ultraviolet light and the first color light, the second color light, and the third color light, in order. While the second filter mechanism retracts the fluorescence observation filter from the optical path, the mixture of the ultraviolet light and the first color light, the second color light, and the third color light, which have passed through the first filter mechanism, are guided by the light guide to irradiate the subject. During the period in which this subject is irradiated or illuminated by the mixture of the ultraviolet light and the first color light, the second color light, the third color light in order, normal subject image data is obtained as color image data, based on image signals obtained by the imaging device. On the other hand, when the second filter mechanism inserts the fluorescence observation filter into the optical path, the mixture of the ultraviolet light and the first color light which has passed through the first filter mechanism is filtered to be pure ultraviolet light and enters the light guide. During the period in which this subject is irradiated by the ultraviolet light, fluorescence image data for the subject is obtained based on image signals obtained by the imaging device.
Alternatively, the second filter mechanism and the first filter mechanism may be arranged along the optical path in this order from the light source side. In this case, whenever the second filter mechanism retracts the fluorescence observation filter from the optical path, the mixture of the ultraviolet light and the first color light, the second color light, and the third color light enter the light guide in order. On the other hand, when the second filter mechanism inserts the fluorescence observation filter into the optical path while the first filter mechanism at the same time inserts the first filter into the optical path, ultraviolet light enters the light guide.
Incidentally, the objective optical system may have a filter for blocking ultraviolet light and an objective lens. Additionally, the filter in such an objective optical system may be an ultraviolet-and-infrared cut-off filter, transmitting visible light while blocking ultraviolet and infrared light.
Further, the fluorescence observation filter may be a filter transmitting the ultraviolet light and either light selected from the second color light and the third color light. In this case, the processor is capable of generating a reference image data based on the image signal obtained by the imaging device during the period in which the second filter or third filter is inserted into the optical path, while controlling the first filter mechanism, with the fluorescence observation filter inserted into the optical path. The processor can then extract specific image data by subtracting the reference image data from the fluorescence image data, and generate diagnostic image data by superimposing the specific image data on the normal image data. Incidentally, this system can be configured to display the portion of the diagnostic image data which corresponds to the specific image data in a specific color, for example, blue on the monitor.
Further, the first filter mechanism may have a first wheel formed in a discal shape into which the first, second, and third filters are fitted, respectively, along its circumference. Moreover, the first filter mechanism may have a motor for rotating the first wheel. Furthermore, the first filter mechanism may sequentially insert each of the filters on the first wheel into the optical path by rotation of the first wheel.
Incidentally, in case the imaging device is a CCD, the illumination time for the illumination light may be adjusted in accordance with the sensitivity of this CCD which varies with the wavelength of the incident light. More specifically, the circumferential length of the filter may be set to compensate the variation of spectral sensitivities of the CCD.
Further, the second filter mechanism may have a second wheel also formed in a discal shape on which the fluorescence observation filter and an opening are disposed along its circumference. Moreover, the second filter mechanism may be equipped with a motor for rotating the second wheel. The second filter mechanism may have a function for sequentially inserting the fluorescence observation filter and the opening into the optical path by rotation of the second wheel.
Incidentally, the light source may be consisted of a lamp and a reflector, or other type of light source. Alternatively, the light source may be composed of light emitting diodes. Further, this endoscope system may have a display device capable of displaying moving picture based on image data selected from normal image data, fluorescence image data, specific image data, and diagnostic image data.